1. Field of the Invention:
This invention generally relates to elastic joints or couplings which are used wherever high radial loads occur at excessive twist angles, such as in transverse control linkages, tilted shaft control linkages, axle struts, spring bearings, link brackets, etc., on, for example, cars, trucks, buses and even rail vehicles. More particularly, this invention relates to an elastic articulation, coupling, or the like, with a metallic inner part, such as a ball or cylindrical sleeve, disposed in an elastomeric body formed of rubber or similar material joined thereto, and in turn being enclosed by a generally cylindrical metallic outer part, such as a cylindrical sleeve, being joined therewith solely by friction through the axial clamping of a pair of annular metallic parts on the end faces of the elastomeric body. On the outer peripheral surface of the elastomeric body, means are additionally provided to enhance the frictional adherence between the outer cylindrical part and the elastomeric body.
2. Description of the Prior Art:
An elastic articulation of the type as generally referred to above is known from German Utility Model No. DE-GM 66 06 532 in which the interior portion forming the rubber-metal part is inserted with the elastic rubber body into the exterior portion and is held within that outer portion by axial bracing. In these conventional joints, structural features are typically located on the outside circumferential surface of the elastic rubber body in order to increase the contact friction between the elastic rubber body and the outer cylindrical member. Typically, techniques used to increase this friction comprise grooves which run axially or circumferentially thereabout. The depth of these grooves is up to one-third the thickness of the rubber. With this technique, when the rubber is compressed, it is also displaced so as to be perpendicular to the grooves. When the grooves are appropriately configured, a more favorable and uniform distribution of compression stress is achieved, therefore resulting in an improvement of the contact friction between the rubber body and the exterior metal portion. However, it has been found that these structural arrangements in known elastic articulations have not invariably led to an adequate increase in frictional adherence. When there is strong axial stressing in clamping of the annular parts, the frictional adherence facilitates only a limited angle of rotation of the elastic articulation. When the maximum permissible angle of rotation is exceeded, the rubber body in the outer part, suffers pronounced abrasion. Accordingly, the known elastic articulations are believed to lack adequate fatigue strength, functional reliability, or desired life expectancy in line with modern requirements. It should also be appreciated, because of the grooves disposed in the elastomeric body that extend relatively deep into the rubber, that there are disadvantageous notching stress peaks in the known elastic joints.
The above identified difficulties are specifically addressed in German Patent Publication Published For Opposition Purposes No. DE-OS 30 04 075, which corresponds to U.S. Pat. No. 4,420,274, which is incorporated herein by reference. This reference cites U.S. Pat. Nos. 3,165,065; 2,705,643; 2,472,029; 2,207,059; and 1,952,115, which are also incorporated herein by reference. This reference, U.S. Pat. No. 4,420,274, teaches an improvement in which a fabric of solid material, preferably metal wire, is imbedded in the peripheral surface of the elastomeric body, with the fabric wire mesh running generally diagonally to the longitudinal access of the coupling, such that the fabric, together with the elastomeric body, are axially compressed and clamped. The fabric, with its meshes running essentially diagonally to the direction of pre-stressing, is yieldable in diameter upon axial compression in camping, such that the fabric advantageously moves uniformly into the metallic outer part. While the surface of the elastic rubber body is thereby strengthened and service life is significantly increased, problems have been encountered with placement in the vulcanizing mold due to the instability of the wire mesh. In addition, further problems arise during manufacture as a result of the fact that the two axial compression discs must be placed in the mold by means of magnets, so that after the vulcanizing mold is closed, it is extremely difficult to maintain important tolerances of the compression discs. Thus, the danger of defects and damage in the end product increases. In addition, after the insertion into the metal exterior portion, only a linear contact exists. This is due to the fact that the wires are laid crosswise on top of one another. After a corresponding length of time in service, wear is caused by the linear contacts, so that ultimately the wire mesh breaks and the joint fails. In addition to the service life difficulties encountered with the joint described in the above-identified U.S. Patent, the manufacture of such a joint requires that appropriate lock washers or locking rings be used to secure the axial compression discs.